The present invention relates to a liquid level detector, and more particularly to an electric liquid level detector of the condenser type for detecting the remaining quantity of liquid stored within a liquid container or tank as accurately as possible.
In a conventional electric liquid level detector of this kind, a float is disposed within a liquid container for vertical movement in response to the variation of the level of liquid stored within the container. The float is provided thereon with a fixed contact which is movable on a resistance element in response to vertical movement of the float to detect the remaining quantity of the stored liquid in dependence upon variation of the resistance value between the fixed contact and one end of the resistance element. In such an electric liquid level detector, relatively large buoyance is required to ensure smooth movement of the fixed contact on the resistance element. This results in difficulty of application of a small size float in the detector. Furthermore, defacement of the two contact elements causes unexpected error in operation of the detector, and also accurate detection of the liquid level may not be expected due to deviation of the detected resistance value caused by difference in contact area between the two contact elements.
In another type of conventional electric liquid level detector, detected is variation of the electro-static capacitance between electrodes submerged into the liquid stored within a container. For the purpose of detecting the level of the stored liquid as accurately as possible, it is required to increase the electro-static capacitance between the electrodes so as to enhance the rate of change of the electro-static capacitance in accordance with variation of the liquid level.